The present invention relates generally to smoke and carbon monoxide detectors. More particularly, the present invention relates to an improved fire detection system.
Fire detectors are commonly used for detecting a fire incident on a particular premise, to include residential and business premises. Commonly used fire detectors are either smoke detectors or temperature sensors. Typically, smoke detectors detect smoke, and cause an alarm to sound in case a fire is detected so that the premises can be evacuated as early as possible or so that other measures can be taken. Smoke detectors are commonly photoelectric or ionization type detectors. The photoelectric sensors use a chamber with a light emitting diode (LED) light source and a photodetector. The photodetector is usually mounted at right angles from the light source. When smoke enters the chamber, the light from the LED is scattered, causing some of the light from the LED source to be sensed by the detector. When the detected light level reaches a set point, an alarm sounds to alert the occupants of the building.
Typically, ionization sensors may contain a small amount of radioactive material in a chamber. When smoke enters the chamber, the radiation from the chamber ionizes the smoke particles, causing the chamber to conduct electric current. The current is measured by a sensing circuit. When the smoke concentration reaches a set point, an alarm sounds to warn observers of the potential hazard.
While these sensors may efficiently detect a fire in some situations, in other situations and other types of fires, the detection may be inadequate. For example, when there is a slow, smoldering fire, the photoelectric type smoke sensor provides faster detection than the ionization type smoke sensor. On the other hand, when there is a fast, open-flame fire, the ionization sensor provides faster detection than the photoelectric type smoke sensor. In addition, these sensors, at times, raise false alarms due to the detection of steam, aerosol spray, and smoke from nuisance smoke sources such as a stovetop, fireplaces, and microwaved products. Some other sensors include features, such as time delay to confirm the presence of fire. Still other conventional fire detectors allow a user to turn off a sounding alarm at the user's discretion.
Still other conventional fire detectors, use temperature sensors to assess the presence of a fire. Fire detectors based on temperature sensors typically measure the rate of increase of temperature in a particular area and raise an alarm if the temperature rise rate is greater than or equal to a threshold rise rate, where temperature rise rate of approximately 15 degrees Fahrenheit per minute (° F./min) is conventionally used. The rate of rise sensor is susceptible to delayed detection of fire.
Conventional detectors are susceptible to false alarms, nuisance alarms, and may be ineffective at early detection depending on the fire type. Improvements in fire detection are desirable to provide efficient, reliable, accurate, and early fire detection.
Further, a fire sensing method that reduces false alarms and provides early detection for many fires and many types of fires is desirable.